In known processes, see for example patent document U.S. Pat. No. 3,606,153, unwanted particles in the atmosphere are discarded by physical and/or chemical means and measures, or are eliminated from the field of vision. Among these processes can be cited the technique of irradiation of the particles by means of sonic and ultrasonic waves transmitted from sound sources from the ground or from a ship towards the particle clouds, mostly fog. The purpose of the acoustic irradiation is to densify and coagulate the particles so as to cause them to settle to the ground due to gravity.
The patent document GB-A-1.154.020 describes an ultrasonic siren for use on board of ships, which transmits two acoustic waves of equal frequency within the range of 16 to 22 kHz, which are phase-shifted by 180.degree.. The intensity of the radiation can be variably adjusted.
When fog is irradiated with frequencies in the audible range, very high acoustic field intensities of at least 150 dB are required in order to achieve satisfactory coagulation of the particles.